drone vs whisper

drone

noun
  • A humming or deep murmuring sound. 

  • One of the fixed-pitch pipes on a bagpipe. 

  • One who performs menial or tedious work. 

  • A person without the ability to think critically and independently, especially one who follows a group blindly; a non-player character. 

  • A remotely controlled aircraft, an unmanned aerial vehicle (UAV). 

  • A Toyota HiAce or a similar van, especially one used by Ugandan state agents to kidnap opposition members. 

  • A male ant, bee or wasp, which does not work but can fertilize the queen. 

  • A genre of music that uses repeated lengthy droning sounds. 

  • A low-pitched hum or buzz. 

verb
  • To speak in a monotone way. 

  • To produce a low-pitched hum or buzz. 

  • To kill with a missile fired by unmanned aircraft. 

whisper

noun
  • A low rustling sound, like that of the wind in leaves. 

  • A private message to an individual in a chat room. 

  • A rumor. 

  • A faint trace or hint (of something). 

  • The act of speaking in a quiet voice, especially, without vibration of the vocal cords. 

verb
  • To speak softly, or under the breath, so as to be heard only by one near at hand; to utter words without sonant breath; to talk without that vibration in the larynx which gives sonorous, or vocal, sound. 

  • To speak with suspicion or timorous caution; to converse in whispers, as in secret plotting. 

  • To make a low, sibilant sound. 

  • To mention privately and confidentially, or in a whisper. 

How often have the words drone and whisper occurred in a corpus of books? (source: Google Ngram Viewer )